Characterization of growing lettuce from density contours—II. Statistics

The density profiles of standing iceberg lettuce are obtained by recording the transmitted X-ray signal during traverse of the row. From the profile of each single head, five parameters are extracted which are used in a regression analysis to predict weight, W, volume, V, and density, D, of the head when stripped for market display. The regression equations are only slightly dependent on variety for 3 varieties tested (Salinas, Monterey, and Great Lakes) and cover a time span of 17 days, from head formation to one week after optimum maturity. Ninety-two, 81 and 80%, of the variation of W, V, and D, respectively, is accounted for by the regression. The distribution of both independent and dependent variables is found to be consistent with a normal distribution. This is one in a series of papers using X-ray scanners to characterize standing row crops.